Thin film magnetic devices are of great importance to industry for storage, such as hard disk drive read heads, and magnetic sensors. In low field applications such as ring magnets, for example, functionality is limited by the lowest magnetic field levels that can be sensed.
One specific technology where permalloy has found good use is in magnetoresistive bridge arrays such as shown in U.S. Pat. No. 6,297,628. In that patent, the permalloy runners are formed in a conventional manner as shown in commonly owned U.S. Pat. No. 5,667,879.
The permalloy runners in the above referenced patents are formed such that the “easy” axis is used. In the prior art, permalloy runner lengths are cut in the wafer level anisotropy direction This axis is called the “easy” axis. The easy axis is in line with the wafer level anisotropy and is always in the direction of the length of the resistor. By contrast, the “hard” axis would be in the width direction and perpendicular to the easy axis. However, permalloy runners such as disclosed in the above referenced patents all are parallel to the wafer level anisotropy direction, which is the easy axis. They are, thus, limited in applications by the level of magnetic field that can be sensed.
Accordingly, it would be of great advantage if a permalloy sensor could be developed with increased sensitivity. Another advantage would be to improve such sensitivity without an increase of size or current consumption. Other advantages and features will appear hereinafter.